Atomically Thin 2D Perovskite/MoS 2 Heterojunctions With Programmable Twist Angle for High‐Performance Photodetection

Twist angle provides a versatile geometric degree of freedom to engineer interfacial coupling and carrier transport in van der Waals heterostructures. However, deterministic control of twist and its quantitative correlation with device performance remain challenging in hybrid perovskite/2D systems. Here, we report a growth‐integrated, in situ strategy to fabricate atomically thin 2D (PEA) 2 PbBr 4 /MoS 2 heterojunctions with programmable twist angles spanning 0° to 60°, establishing twist as a reproducible device parameter. Twist‐resolved Raman and photoluminescence mapping reveal registry‐dependent interlayer coupling, while x‐ray photoelectron spectroscopy and density functional theory demonstrate twist‐tunable charge transfer and electronic reconstruction. Photodetection and transport exhibit a pronounced nonmonotonic dependence on twist angle, with an intrinsic optimum at 30°. The 30°‐(PEA) 2 PbBr 4 /MoS 2 heterojunction exhibits ultrahigh photoresponsivity of 34 A W −1 , a specific detectivity of ∼2.5 × 10 12 Jones, an I on /I off up to 4.5 × 10 6 , and effective field‐effect mobility of 182.5 cm 2 V −1 s −1 under 405 nm laser illumination, reflecting maximized interfacial synergy. Our work provides theoretical insights into the design of perovskite/TMD heterojunction electronics by establishing a quantitative relationship between twist angle and optoelectronic performance in the (PEA) 2 PbBr 4 /MoS 2 system, offering guidance for the optimization of high‐gain photodetectors and low‐power switching devices.